Removal of metal contaminants from heavy oils by hydrogenation followed by solvent extraction



Aug. 5 1958 H. BIEBER ET AL REMOVAL OF METAL C ONTAMINANTS FROM HEAVY OILS BY HYDROGENATION FOLLOWED BY SOLVENT EXTRACTION Filed March 6. 1956 LIGHT GASES SOLVENT /SEPARATION SOLVENT RECOVERY 5 v TREATED on.

D SOLVENT} /EXTRACTION SOLXENT HEAVY HYDROTREATING '2 SOLVENT HYDROGEN VII 'RECOVERY REJECTED IMPURITIES Herman Bleber Inventors Harry M, Harfzband REMOVAL OF METAL CONTANTS FROM HEAVY 6H5 BY HYDRQGENATIGN FOLLOWED BY SOLVENT EXTRACTHlN Herman Bieher, New York, N. Y., and Harry M. Hartshand, Westfield, N. 3., assignors to Esso Research and Engineering Company, a corporation of Delaware Application March 6, W56, derial No. 569,705

2 Claims. (Ql. 196-35) The present invention relates to an improved process for the removal of metal contaminants, ash, and other impurities from heavy oils. It is more particularly concerned with an improved two-step process involving hydrotreating and liquid-liquid extraction for removal of contaminants from crude oils and residua to obtain improved fuel oils or cracking feed stocks. For example, vanadium, a source of corrosive ash in bunker fuels, and nickel, a catalyst poison in gas oils, are removed according to this invention.

In brief compass, this invention proposes to remove metal contaminants from a heavy oil by first hydrotreating the oil, and then extracting contaminants therefrom using a selective solvent.

It has been known that extraction processes,- e. g., a phenol extraction process, will remove impurities such as metal contaminants and coke formers from heavy oils such as crudes and residua. The extent of removal of impurities, particularly from a crude or residual oil, has not been, however, nearly as effective as desired. Extraction removes only about 10 to of the metal contaminants.

It has now been discovered that there is an unexpected advantage to be gained by first mildly hydrotreating an oil before extraction of contaminants. It has now been found that with a heavy oil, when first hydrotreated and then extracted with a suitable solvent, the extent of metal contaminants removal is far greater than would be expected from previous experience.

The types of metal contaminants present in heavy oils may be classified as those that are volatile and extractable (class I), and those that are non-volatile and non-extractable (class II). it is commonly believed that most of the metal contaminants present in heavy oil are associated with a porphyrin type of molecule or class of compounds (metallo-porphyrins).

Metallo-porphyrins are usually resistant to chemical breakdown and thermal decomposition, and some, e. g.,

nickel and vanadium, are extremely resistant. The class I contaminants are believed to be of the simple porphyrin class of compounds (monomers) and are readily removed from oils by extraction. Attempts to remove, by extraction, the class II types of metal contaminants, which are believed to be polymers (dimeric or polymeric) of porphyrins have previously been unsuccessful.

The present invention is predicated upon the discovery that during mild or moderate hydrotreating of heavy oils, class II metal contaminants are converted to the extractable class I type. The hydrotreating is not carried out to an extent sufficient to cause appreciable or complete degradation of the class 11 compounds. While not being limited, of course, to this theory, a possible explanation may be that sulfur linkages account for the polymeric structure of the class II compounds and that during mild hydrogenation of the oil, sulfur is removed thereby destroying the sulfur linkages and leaving an extractable monomer type of metal contaminant.

2,846,358 Fatented Aug. 5, 1958 The present invention, based upon this discovery, comprises relatively mild hydrotreating of a heavy oil followed by liquid-liquid extraction to obtain a surprisingly high degree of metal contaminant removal, besides improving other properties such as lowering the nitrogen, sulfur, MNI and Conradson carbon contents. In some cases the hydrotreating step may be preceded by an additional extraction or asphalt precipitation step.

The following explanation of the drawing attached to and forming a part of this specification will serve to make this invention clear. The drawing schematically depicts a simplified version of this process.

In light of the above explanation, it can be seen that this invention is primarily applicable, and is limited in utility, to heavy oils containing constituents non-vaporizable at atmospheric pressure, such as petroleum crudes, shale oils, tar sands, asphalts, tars, etc., and residua therefrom. Well fractionated distillate oils usually contain only class I metal contaminants which are volatilizable and readily extractable. Most distillate oils, being free of non-vaporizable constituents, do not require, therefore, the presently proposed treatment.

The hydrotreating process as used in the present ,in vention comprises one where the heavy oil is contacted under mild hydrogenation conditions in the presence of a hydrogenation catalyst, preferably a catalyst that is resistant to sulfur contamination. Hydrogenation catalysts such as platintun, palladium, nickel, vanadium, etc. can be used, although cobalt and/or molybdenum are preferred. Mixtures of catalysts may be used, and the catalyst may exist as an oxide or sulfide. Promoters such as fluorine, chlorine, rare earth, etc., can be used.

These catalysts may, of course, de distended on suitable carriers such as natural or synthetic aluminas, silicas, metal hydrides, etc. be deposited on the carrier in place if desired. For example, V O obtained from the feed oil itself, can be deposited on an alumina base in the reactor and used as a catalyst. The catalysts can be used in the form of fixed, fluid, or gravitating beds, or be used in a suspensoid or slurry type of process. The catalysts can be used on a once-through basis or can be regenerated continuously or intermittently, either within or externally of the unit by burning, hydrotreating, chemical treating, reworking, etc. It is preferred to use a fixed bed type of hydrotreating unit with periodic oxygen regeneration of the catalyst.

With the preferred sulfur resistant catalysts, e. g., a cobalt molybdate catalyst, therange of hydrotreating The solvent extraction step involves contacting, preferably countercurrently in a staged unit, the hydrotreated oil with a selective'solvent to obtain a raffinate and an extract phase; and recovering solvent for reuse and product from these phases. The contacting may be effected in a plate, packed or positive mechanical mixing tower (e. g., Scheibel tower), or similar units known in the art. The solvent used is one having an affinity for aromatic and nitrogen type compounds and is preferably one that is predominantly selective to the class I type of highly aromatic metal contaminants. Preferred solvents include: butyrolactone, phenol, furfural, pyridine, acetic acid saturated with bromine, and dimethylsulfoxide.

Preferred solvent extraction conditions are:

Temperature F to 300 Oil solvent ratio 1:1 to 4:1

The catalytic component can of a hydrogenation sulfur resistantcatalyst. Y The catalyst is in theforrn of particles having a size in the =range of to 14 mesh. A free hydrogencontaining gas, contain ing preferablyover 50 volume percent hydrogen, isin troduced into the base of zone 2 by line 3. The zone-is 10 maintained under mild hydrotreating conditions.- The conditions are such that any substantial conversion of I class 11 contaminants to free metals is avoided, because this results in rapid deactivation of the catalyst, 1owyields, andexcessive hydrogen consumption.- The treated oil is removed by line 4 and passed to a separationzone 5.- Somedistillate gas oils and naphtha, formed during the hydrotreating, can be removed in zone 5 butas shown, it is simply used to separate light gases, which are removed by line 6. The remainder ofthe hydrotreated liquid product is passed from separation zone 5 by line= 7 to the bottom of a conventional extraction zone 8,

which may comprise a tower containing a plurality of vertically spaced perforated plates. A suitable solvent, e. g., phenol, is admitted to the top of the tower by line 9, and flows countercurrently to the oil, extracting metal con-- taminants-and other undesirable constituents. The solvent and impurities are removed from the baseof tower 8 by line 10 and sent to a solvent recovery zone '11 which" may comprise a distillation or steam stripping zone.- Solvent is removed from zone 11 by line 12 for reuse. The impurities rejected from the oil are recovered fromzone 11 by line 13 and may be disposed of asdesired.

The raffinate from zone 8 is recovered over-head via line 14 and passed to a solvent recovery zone 15,.similar. to

zone 11. Separated solvent is removed for reuse from zone 15 by line 16, and the treated oil is recovered by line 17. Besides having an extremely low metals content,thisoilis greatly improved in other respects, i. e., sulfur-,- nitrogen, Conradson carbon and aromatic contents, etc.-

have been substantially reduced. This oil product in line 17, depending upon the feed stock, may be used asa fuel-- oil-and will be superior in this respect because of its extremely low ash content. It will make an excellentfeed stick for catalytic cracking or lube oil manufacturing proc-= esses.

EXAMPLE 1 The following data were collected todemonstrate the surprising results obtained by the presentinvention. Thesame feed stock was used for each of the three examples.

and comprised a residuum from Bachaquero crudehaving the following inspections:

Initial boiling point 1000 Percent on crude 31.

Gravity 1.9 A. P. I. Sulfur 3.78 percent. Conradson carbon 32 wt. percent. 7

4 p. s. i. g., 17.1 wt. percent conversion to l100 F.on feed, and 3440 s. c. f. of added hydrogen/bbl. The catalyst was 13% C0MoO carried on spray dried alumina, with 5% fluorine added.

The extraction of the oils was carried out on a labora tory bench scale basis in a flask. Five successive batch contacts were made at 150 F. using each time 100 vol. percent (on oil) pyridine and 20 vol. percent water.

Table I After Hy- Pyridine After Hydrotreat- Process None Extracdrotreating and tion Only ing Pyridine Extraction Yield, Wt. Percent 100 95 90 Metals, p. p. m.:

Ni 136 70 5 501 24 12 a 10 Probably mostly insoluble rust.

The above table shows that for the same yield loss in each step, the combination process according to this invention removed 96.6% of the nickel and 98% of the vanadium at a yield of 90%. This is to be compared with the only 10% vanadium removal for extraction alone, and the 58% vanadium removal for hydrotreating alone. Frornprevious experience it is known that hydrotreating'orextracting to a yield of 90% does not even approach the extent of removal obtained by the combined steps. Optimum conditions were not maintained by these tests. By slightly altering the hydrotreating and/or extraction conditions, essentially complete metal and ash removal can be accomplished.

Having' described this invention and presented specific examples thereof, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. A process for improving the quality of heavy oils containing constituents'non-vaporizable at atmospheric pressure which comprise mildly catalytically hydrogenatingsaid oil in the presence of hydrogen and a sulfur resistantcatalyst at a pressure in the range of 200 to 2000 p.-s. i., a temperature in the range of 600 to 950 F., aspacevelocity-of 0.25 to 4.0 v./v./hr. and a hydrogen partial pressure of 100 to 2000 p. s. i. to convert nonvolatile and non-extractable polymeric metal contaminants to volatile and extractable monomeric compounds, and treating'the hydrogenated product with a solvent selected from the group consisting of butyrolacetone, phenol, furfural, pyridine, acetic acid saturated with bromine, and 'dimethylsulfoxide to remove the extractable monomeric compounds.

2. The process of claim 1 wherein said catalyst is in the form of a fixed bed in a hydrogenation zone, and is periodically oxidatively regenerated.

References Cited in the file of this patent UNITED STATES PATENTS 1,932,369 Guthke Oct. 24, 1933 2,393,288 Byrns Jan. 22, 1946 

1. A PROCESS FOR IMPROVING THE QUALITY OF HEAVY OILS CONTAINING CONSTITUENTS NON-VAPORIZABLE AT ATMOSPHERIC PRESSURE WHICH COMPRISES MILDLY CATALYTICALLY HYDROGENATING SAID OIL IN THE PRESENCE OF HYDROGEN AND A SULFUR RESISTANT CATALYST AT A PRESSURE IN THE RANGE OF 200 TO 2000 P. S. I., A TEMPERATURE IN THE RANGE OF 600* TO 950*F., A SPACE VELOCITY OF 0.25 TO 4.0 V./V./HR. AND A HYDROGEN PARTIAL PRESSURE OF 100 TO 2000 P. S. I. TO CONVERT NON- 